Numerical Simulation of Droplet Impact, Spreading and Penetration onto Curved Porous Media

Droplet impact on curved porous media involves coupled spreading, wrapping, recoiling, and penetration. A three-dimensional level set model was developed in COMSOL and validated using high-speed imaging experiments to quantify axial and circumferential spreading lengths, central liquid film height, penetration depth, and energy partitioning at maximum spreading. As the We increased from 10 to 40, the maximum axial and circumferential spreading factors increased by 15.58% and 25.80%, respectively, while viscous dissipation increased by 17.32% and the recoiling-stage peak central liquid film height decreased by 16.70%. Increasing porosity from 0.4 to 0.6 had little effect on macroscopic spreading but raised the penetration peak and reduced the recoiling-stage liquid film height by 18.25%; similarly, increasing particle diameter from 0.15 to 0.25 mm increased the penetration depth at 20 ms by 49.75%, by reducing Darcy–Forchheimer resistance. Increasing surface tension from 0.0273 to 0.1092 N/m reduced the peak axial and circumferential spreading factors by 26.08% and 36.49%, respectively, whereas increasing viscosity from 0.003 to 0.009 Pa·s reduced the peak axial spreading factor and penetration peak by 15.96% and 45.95%. These results demonstrate that pore-scale parameters and liquid properties jointly regulate droplet impact on curved porous media, with pore structure affecting penetration and liquid properties controlling spreading and recoiling.